Modular screen

ABSTRACT

A modular screen for classifying materials comprising a screen cloth supported on a frame, said frame comprising a plurality of modular side frame sections and a pair of cross members at opposite ends interconnecting the outer ends of the end ones of said modular side frame sections; each of said side frame sections having a pair of precisely parallel enlarged opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therewith whereby the area of the screen frame can be changed by the addition or subtraction of pairs of modular side frame sections.

45] Mar. 19, 1974 United States Patent Kauffman I l MODULAR SCREEN [75] Inventor:

1,856,450 5/1932 209/414 X l,839.6l4 l/l932 Primary Examiner-Richard A. Schacher Assistant Examiner-Gene A. Church Simpson, Trustee, both of Chicago, Ill.

ABSTRACT A modular screen for classifying materials comprising a screen cloth supported on a frame, said frame com- 22 Filed: Nov. 29, 1972 [21] Appl.No.:310,393

prising a plurality of modular side frame sections and 209/85 2'09/402 209/4l 3 a pair of cross members at opposite ends interconnect- Int. 1367b 13/04 ing the Outer ends of the end ones of Said modular Side 2O9/8'5 401 frame sections; each of said side frame sections having Field of Search 402, 404,

a pair of precisely parallel enlarged opposite end faces 55/482 483, 484 adapted to be secured to the end face of an adjacent section in end to end relation therewith whereby the area of the screen frame can be. changed by the addition or subtraction of pairs of modular side frame sections.

References Cited UNITED STATES PATENTS 14 Claims, 4 Drawing Figures 24 Ol 44 99 0O 22 my u fV uo BL 54 40 99 ll 67 3O 65 86 76 3 7 2 MODULAR SCREEN- The present invention relates to a new and improved screening apparatus for use in classifying materials such as bulk granular and particulate materials and wet slurries and the like. The screen is designed on a modular basis so that a screen area of a particular value may be obtained by grouping together standard size section modules in desired numbers. Oftentimes in industrial applications it is extremely difficult to degisn and engineer in advance or accurately forecast how much screen area will be required to provide the required screening action for a process flow of material. The

flow rates often change as well as the type and consis- I tency of materials and these factors are not always accurately forecasted in advance.

Many times after a particular size of screen has been ordered and installed it becomes desirable to increase the size of the screen to handle an additional load or flow rate of material or in the alternative, it is sometimes desirable to reduce the size of a screen for space reasons when it is determined that the screening capacity selected is too large for the flow rate of a particular application. It is therefore an object of the invention to provide a new and improved modular screening apparatus having a plurality of modular sections of standard size and configuration which sections may be added or deleted from an assembly of the same to adjust the size and capacity of the screening apparatus as needed.

Another object of the invention is to provide a new and improved modular screening apparatus of the character described wherein the screen includes a frame which has side structural members made up of one or more side section modules joined in end to end relation to provide a desired frame length for the'screening apparatus.

Another object of the present invention is to provide a new andimproved modular screening. apparatus of the character described including a frame having modular side sections, each having means thereon for supporting a component of a screen vibrating apparatus.

Another object of the present invention is to provide a new and improved modular screening apparatus of the character described having new and improved means for vibrating the screen cloth.

Another object of the present invention is to provide a new and improved modular screen apparatus of the character described wherein additional frame section modules are readily added or deleted to change the effective capacity after the screen has been initially set up or installed in place.

Another object of the present invention is to provide a new and improved modular screening apparatus of the character described which can be shipped in a knocked down condition including small-size packages containing modular components ready for assembly at the operating site with a minimum of time and labor being required for assembly. In this connection it should be noted that a large size screen for example, a screen 8' wide X 15 long might take a special type of carrier for shipment, whereas a modular screen in accordance with the present invention having the same capacity can be shipped in a routine manner because of its smaller size packages containing the components in a knocked down condition.

These and many other objects and advantages of the present invention are accomplished in an illustrative embodiment comprising a screening apparatus having a screen cloth supported for vibration on a frame. The said frame includes a plurality of similar modular side frame sections of standard size and shape and a pair of cross members at opposite ends interconnecting the outer ends of said side frames. Each side frame section includes a pair of precisely parallel enlarged opposite end faces which are adapted to be secured to the end face of an adjacent section in end to end relation, or to one end of a cross member. Any number of modular side frame sections can be connected together to provide a screen frame of desired length and a number of different length cross members are provided to provide a variety of screen widths.

For a better understanding of the invention reference should be had to the following detailed description when taken in conjunction with the drawings in which;

FIG. 1 is a side elevational view of a new and improved modular screening apparatus in accordance with the present invention;

FIG. 2 is a fragmentary, transverse sectional view through the screening apparatus of FIG. 1 taken substantially along lines 22 thereof;

FIG. 3 is atop plan sectional view with portions broken away taken substantially along lines 3-3 of FIG. 1, and

FIG. 4 is a side elevational view like FIG. 1 showing structure for attachment of the screen cloth to the modular frame of the screen.

Referring now more particularly to the drawings therein is illustrated a new and improved modular screen apparatus for use in sizing or sifting a wide variety of bulk type materials including particulate materials, wet slurries and the like. The screening apparatus is generally referred to by the reference numeral 10 and is usually installed on a slope as shown in FIG. 1. Material to be screened or size classified is introduced onto the upper end of the screen through an inlet or supply chute 12 (dotted lines), and flows downwardly over a screen cloth or mesh surface defining sized openings toward the lower end of the screen where the oversize material is discharged through an oversize discharge chute 14. The on size material passing through the screen cloth or mesh is collected in a hopper 16 attached to the underside of the screen, and in the case of dusty or time materials, a hood or enclosure 18 may be provided above the screen cloth to prevent excessive dust from entering the atmosphere and to prevent spillage of material from the sides of the screen.

In accordance with the present invention the screening apparatus 10 includes a screen cloth 20 generally formed of woven stranded material with openings of the desired size therein for classifying the material being sifted. The screen cloth is supported on a rectangular frame 22 (best shown in FIG. 3) which comprises a pair of end cross members 24 formed of steel plate or other material of suitable strength for the dimensions involved.

In accordance with the present invention the frame 22 comprises a plurality of modular segments labeled A, B, C etc. which modular segments are identical to one another and are joined together to make up the complete screen frame. Any desired number of modular segments may be interconnected in series to provide a desired frame length and if a shorter length is required individual modules may be removed or disconnected. Each modular segment includes a left hand side frame section module 26 and an opposite, parallel spaced apart, right hand modular side frame section 28. The left and right hand module sections are spaced apart laterally by a dimension determined by the length of a pair of end cross members or tie plates 24. The respective left and right hand module side sections 26 and 28 are joined in end to end relation to provide left and right longitudinal sides of the rectangular frame 22. Preferably the modules 26 and 28 are formed of metal in a casting process and are dimensioned to provide suitable strength characteristics. Because all of the left hand sections 26 and the right hand sections 28 are identical, only two different mold patterns are required regardless of the assembled size of the completed frame 22. For example, the modular side frame sections 26 and 28 are approximately two feet in length and when assembled in end to end relation, frame lengths 2, 4, 6 and 8 or any multiple of 2 are available. Similarly, the end cross members or tie plates 24 are available in several standard widths such as 2', 4', 6', 8 etc. as desired. When a large number of side frame sections are joined together in end to end relation, one or more intermediate cross members or tie plates 24 are provided in between the outer end cross members to provide rigidity and strength.

AS viewed in FIGS. 1, 2 and 3, the left hand modular frame sections 26 include a rectangular side wall 30 with an outwardly extending continuous flange 32 around the peripheral edges thereof (best shown in FIG. I). The flange 32 forms a rectangular housing or enclosure 34 which is open toward the outside of the side frame and these housings or enclosures are adapted to contain and hold components of the screen vibrating mechanism of the screening apparatus. As best shown in FIG. 2 the peripheral flange 32 includes a relatively wide upper flange 36 along the upper edge of the side wall 30, and a relatively narrow, lower flange 38 along the lower edge. At opposite ends the flanges 36 and 38, as well as the side wall 30, are integrally joined with trapezoidal shaped end flanges 40, each having a precisely machined planar outer end face adapted to abut and be secured to the adjacent outer end face on the flange 40 of the next adjacent modular side frame section 26 in the frame assembly. The outer faces of the end flange sections 40, on the outer module segments A and D (FIG. 1) are adapted to abut and are secured to the end cross members or tie 24.

The outer end surfaces of the end flange sections 40 of each modular side frame section 22 are machined to be precisely parallel to one another and normal to the side wall section 30 so that any number of side frame sections may be joined together by means of removable bolts 42 to provide a structurally strong left hand side for the rectangular frame 22 of the screening apparatus 10. To this end, the end flanges 40 are drilled with accurately positioned holes to facilitate accurate, end to end alignment of the section during assembly. Similarly, the end cross members 24 are drilled with precisely positioned holes to accommodate bolts 42. As best shown in FIGS. 1 and 2 the modular side frame sections 26 are substantially channel shaped in transverse cross section to provide high strength with a relatively low weight. Similarly as viewed in FIG. 3 the sections 26 are channel shaped in cross section with the side wall sections 30 as the web of the channel.

In accordance with present invention, the rectangular side walls 30 extend upwardly above the level of the upper flange sections 36 as best shown in FIG. 2 and the upwardly extending portions are provided with a recessed shoulder 44 adapted to accommodate the lower edge portion of the screen hood 18. The modular side frame sections 26 are also provided with inwardly directed segmented flanges 46 adapted to support the outer side edge portion of the screen cloth 20 which rests thereon as best shown in FIG. 2. If desired, the screen cloth 20 may be positively secured to the flange 46 by means of suitable fasteners. The lower flanges 38 of the modular side frame sections 26 provide flange means for supporting attachment with an upper edge flange of the hopper 16 as best shown in FIG. 2 so that installation of the modular screening apparatus 10 on a hopper is relatively simple.

The left hand side frame sections 26 are provided with a transversely inwardly extending flanges 48 at opposite ends, each formed with a precisely positioned opening therein for accommodating a bolt 42. These end flanges are integral with the end flanges 40 and are machined with the outer end face coextensive therewith. The modular right hand side frame sections 28 are generally similar in construction to the left hand sections 26 and include a rectangular side wall section 50 with an outwardly extending continuous flange 52 around the periphery thereof. The flange 52 defines a rectangular, outwardly open enclosure or housing 54 for accommodating components of the mechanism for vibrating the screen cloth 20 and includes an upper flange section 56, a parallel lower flange section 58 and a pair of opposite end flanges 60, all integrally joined together as cast. AS best shown in FIG. 2, the upper flange section 56 and lower flange section 58 are of substantially equal width and the end flanges 60 are rectangular in shape rather than trapezoidal like the left hand end flanges 40. Each end flange 60 is provided with a machined outer end face adapted to abut and be secured to the end face of an adjacent right hand side frame section 28 or an end cross member 24. The sides 50 of the right hand modular section 28 project upwardly above the level of the upper flanges 56 and are formed with an outer recessed shoulder 64 for accommodating a lower edge portion of the right hand side of the screen enclosure housing 18 as best shown in FIG. 2.

The right hand side frame sections are provided with inwardly extending segmented upper flanges 66 for supporting the side edge of the screen cloth 20 as best shown in FIG. 2. Each section 28 includes a pair of transversely inwardly extending small end flanges 68 to provide additional strength for a group of right hand side frame sections joined end to end with bolts 62 interconnecting the end flanges. After a string of right hand modular side frame sections 28 are bolted together in end to end relation, the resulting side frame structure is strong and is precisely aligned in parallel with the string of left hand modular side frame sections 26 on the opposite sides of the frame 22.

' end relationas side frame members. Cast modular side frame sections with precisely machined end surfaces provide advantages over conventional fixed size welded screen frames which tend to warp during welding and which are difficult to straighten after welding or when subjected to screen tension. In addition, welded screen frames do not lend themselves readily to changes in size as do the modular cast side sections 26 and 28 of the present invention.

In accordance with the present invention each of the screen section modules A, B, C, D etc. used in making up a screen of a particular size includes one left hand modular side frame section 26 and a right hand modular side frame section 28.'The side wall sections 30 and 50 are in precise parallel arrangement and the end cross members 24 or intermediate tie members are provided to provide the desired spacing between the left and right hand assembled side frame sections.

After a rectangular frame 22 is assembled from a member of the section modules 26 and 28, the screen cloth 20 is installed and for this purpose the upper end cross member 24 is provided with an elongated angle 70 having a flange with a re-entrant end adapted to eninner edge portion of an adjustable strip 76. The screen attachment strip is supported from the lower end cross member 24 by adjusting bolts 78 which have hooked ends projecting through slotted openings in the strip. Threaded outer ends of the bolts are secured by adjusting nuts 80 adjacent the outside surface of the lower end member 24. The screen cloth 20 can thus be tensioned longitudinally by adjustment of the nuts 80 on the bolts 78 and if desired, longitudinal side edges of the screens can be fastened or secured with cap screws or the like projecting downwardly into threaded apertures provided in the inwardly extending segmented upper flanges 46 and 66 on the respective left and right hand modular side frame sections 26 and 28.

In accordance with the present invention, each modular screen segment A", B, C, D etc. in the screening apparatus is provided with a separate vibrator mechanism for moving the screen cloth 20. The vibrators are referred to generally by the reference numeral 82 (FIGS. 2 and 3), and each includes an elongated striker bar 84 having an elongated U-shaped strip 86 formed of resilient material such as rubber or the like adapted to engage and bear'against the underside of the screen cloth as best shown in FIGS. 1 and 2. If the U-shaped strips wear out they are easily replaced and these resilient members are adapted to cushion the shock and reduce frictional wear on the underside of the screen cloth 22. The striker bar 84 is supported from an elongated hollow tubular shaft 88 by means of a plurality spaced apart radially outwardly extending arms 90 (as best shown in FIG. 1), and the arms are relatively broad at their inner ends joined to the tubular shaft and are thinner adjacent their outer ends attached to the striker bar 24. The shaft 88 is supported at opposite ends by a pair of outwardly extending stub axles 92,

- each having an annular collar 93 adapted to be inserted into the outer end of the hollow shaft. The stub axles 92 project outwardly through preformed circular openings 36a and 66a formed in the respective modular side frame sections 26 and 28 and the outer ends of the axles are supported for oscillatory rotation on bearing block assemblies 94 secured to the underside of the upper flanges 36 and 56 of the respective left and right hand side frame sections.

AS best shown in lllG. 2 it will be seen that the bearing blocks 94 are mounted within the enclosures 34 and 54 formed in the side frame sections and thus are shielded from a lot of stray material which may be present around the screen. Each bearing block is secured to its respective supporting flange by means of a pair of elongated cap screws 96 threaded into bores provided in the flanges as best shown in FIG. 2. The left hand stub axles 92 (FIG. 2) project outwardly beyond the bearing block assemblies 94 to support one end of a rocker arm secured thereto. The other ends of the rocker arms are pivotally connected to the armatures MM) of electromagnetic vibrators 102 which are mounted on the upper surface of the flanges 36 on the sections 26. Electrical power is supplied to the electromagnetic vibrators lltl2 on an individual basis and cause the armatures 100 to vibrate and reciprocate longitudinally in order to rock the arms 98 and cause the stab axles 92 to oscillate back and forth. As the stub axles 92 and hollow shafts 88 oscillate, the striker bars 84 and the resilient members 86 thereon moves up and down against the underside of the screen cloth 20 to provide vibratory screening action as the material flows over the screen cloth.

Preferably the vibrators 102 are of the type which may be adjusted to provide the desired amount of vibratory power in terms of armature stroke amplitude and frequency for a particulate material being screened. it should also be understood that, if not required, a vibrator assembly 82 for a particular modular screen segment A, B, C, C etc. may be omitted. Because all of the left and right hand modular side frame sections 26 and 28 are made to accommodate the components of a vibrator assembly 82, the openings 30a and 56a in the side frame wall sections may be closed with suitable removable plugs when no vibrator is provided for a particular segment and the plugs may be removed if a vibrator is added at a later date. Similarly, mounting holes for the bearing blocks 94 and the electromagnetic vibrators 102 are provided on all of the sections 26 and 28 and the flanges 36 are formed with threaded openings for receiving the mounting bolts 96 and bolts 104 for securing the vibrators in place. Likewise the flanges 36 of the sections 26 are formed with an opening 36a to accommodate a downwardly depending armature we of an electromagnetic -vibrator 102.

From the foregoing it will be seen that the novel screening apparatus 10 of the present invention comprises a modular system wherein any number of screen section modules A, B, C, D may be assembled or diassembled at an installation or job sight to provide a frame 22 of the desired area to fit a particular screencloth 26. Screen area can be changed as requirements change in an efficient manner simply by adding or subtracting modules or using cross members 24 of different length. A screen of the present invention need never be put out of service because of too high or too low capacity because the area of screen can be readily changed to suit changing needs.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A screening apparatus for classifying particulate materials and the like comprising a screen cloth supported on a frame, said frame comprising a pair of parallel spaced apart side members, each side member including a plurality of modular side frame sections in end to end relation and at least one pair of cross members at opposite ends interconnecting the outer ends of end ones of said modular side frame sections, each of said frame sections having a pair of precisely parallel enlarged, opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therewith.

2. The screening apparatus of claim 1 wherein said modular side frame sections are formed of cast metal and said precisely parallel opposite end faces are formed after casting in a machining operation.

3. A screening apparatus for classifying particulate material and the like comprising a screen cloth supported on a frame, said frame comprising a plurality of modular side frame sections and a pair of cross members at opposite ends interconnecting the outer ends of end ones of said modular side frame sections, each of said side frame sections having a pair of precisely parallel enlarged, opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therwith, and each of said side frame sections including a side wall and an integral outwardly extending peripheralflange along the edges thereof, said precisely parallel opposite end faces formed on oppositely outwardly facing end portions of said flange.

4. The screening apparatus of claim 3 wherein said modular side frame sections include integrally formed inwardly extending flanges along the upper edge for supporting the edge of said screen cloth.

5. A screening apparatus for classifying particulate materials and the like comprising a screen cloth supported on a frame, said frame comprising a plurality of modular side frame sections and a pair of cross members at opposite ends interconnecting the outer ends of end ones of said modular side frame sections, each of said side frame sections having a pair of precisely parallel enlarged, opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therewith, and each of said modular frame sections comprising at least one pair on opposite sides of said frame, and screen vibrating means extending between the opposite sections of said pair including opposite ends supported from said sections.

6. The screening apparatus of claim 4 including a pair of inwardly extending end flanges at opposite ends of said side wall, said end flanges including outer surfaces forming portions of said precisely parallel opposite end faces.

7. The screening apparatus of claim 6 including removable fastening means for securing together the end flanges and end portions of said peripheral flange on adjacent end to end modular 'side frame sections.

8. The screening apparatus of claim 6 wherein said screen vibrating means comprises a pair of bearings mounted on the peripheral flange of opposite side frame sections of said pair, a shaft supported by said bearings, means carried on said shaft for engaging said screen cloth to vibrate the same upon oscillatory rotation of said shaft, and means on one of said side sections of said pair for oscillating said shaft.

9. The screening apparatus of claim 1 wherein said modular side frame sections include a side wall and an inwardly extending flange along the upper edge of said side wall for supporting the longitudinal edge of said screen cloth, and tension means connected between opposite ends of said screen cloth and the adjacent cross member for exerting adjustable longitudinal tension on said screen cloth.

10. The screening apparatus of claim 9 including a screen vibrating mechanism supported by a pair of opposite modular side sections on opposite sides of said frame, said mechanism including means engaging the under side of said screen cloth for vibrating the same up and down.

11. A screening apparatus for classifying materials comprising a screen cloth supported from a frame of variable size, said frame comprising a pair of end cross members interconnecting the ends of a plurality of pairs of modular side frame sections on opposite sides of said frame joined end to end,'each side frame section including a side wall and a pair of end walls having parallel outer end faces normal to said side wall, and screen vibrator means supported from a pair of opposite side frame sections independent of other sections.

12. The screening apparatus of claim 11 wherein each modular side frame section has a channel shaped cross section including a pair of upper and lower flanges extending outwardly of the edges of said side wall and joined at opposite ends with said end walls forming an outwardly opening enclosure, said screen vibrating means including an oscillatory shaft extending between opposite side frame sections and a pair of bearings supporting opposite ends of said shaft mounted in said enclosures of said opposite side frame sections on a portion of the flange thereof.

13. The screening apparatus of claim 12 wherein said vibrator means includes a reciprocating vibrator mounted on the flange of one of said pairs of opposite side frame sections and connector means interconnecting said vibrator and an end portion of said shaft to rotatively oscillate the same upon reciprocation of said vibrator.

14. The screening apparatus of claim 13 wherein said bearings are mounted on the underside of said upper flanges and said vibrator is mounted on the top of an upper flange, said vibrator including a reciprocating armature extended through an opening in said upper flange and pivotally connected at its lower end to said connector means.

* t t k 

1. A screening apparatus for classifying particulate materials and the like comprising a screen cloth supported on a frame, said frame comprising a pair of parallel spaced apart side members, each side member including a plurality of modular side frame sections in end to end relation and at least one pair of cross members at opposite ends interconnecting the outer ends of end ones of said modular side frame sections, each of said frame sections having a pair of precisely parallel enlarged, opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therewith.
 2. The screening apparatus of claim 1 wherein said modular side frame sections are formed of cast metal and said precisely parallel opposite end faces are formed after casting in a machining operation.
 3. A screening apparatus for classifying particulate material and the like comprising a screen cloth supported on a frame, said frame comprising a plurality of modular side frame sections and a pair of cross members at opposite ends interconnecting the outer ends of end ones of said modular side frame sections, each of said side frame sections having a pair of precisely parallel enlargeD, opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therwith, and each of said side frame sections including a side wall and an integral outwardly extending peripheral flange along the edges thereof, said precisely parallel opposite end faces formed on oppositely outwardly facing end portions of said flange.
 4. The screening apparatus of claim 3 wherein said modular side frame sections include integrally formed inwardly extending flanges along the upper edge for supporting the edge of said screen cloth.
 5. A screening apparatus for classifying particulate materials and the like comprising a screen cloth supported on a frame, said frame comprising a plurality of modular side frame sections and a pair of cross members at opposite ends interconnecting the outer ends of end ones of said modular side frame sections, each of said side frame sections having a pair of precisely parallel enlarged, opposite end faces adapted to be secured to the end face of an adjacent section in end to end relation therewith, and each of said modular frame sections comprising at least one pair on opposite sides of said frame, and screen vibrating means extending between the opposite sections of said pair including opposite ends supported from said sections.
 6. The screening apparatus of claim 4 including a pair of inwardly extending end flanges at opposite ends of said side wall, said end flanges including outer surfaces forming portions of said precisely parallel opposite end faces.
 7. The screening apparatus of claim 6 including removable fastening means for securing together the end flanges and end portions of said peripheral flange on adjacent end to end modular side frame sections.
 8. The screening apparatus of claim 6 wherein said screen vibrating means comprises a pair of bearings mounted on the peripheral flange of opposite side frame sections of said pair, a shaft supported by said bearings, means carried on said shaft for engaging said screen cloth to vibrate the same upon oscillatory rotation of said shaft, and means on one of said side sections of said pair for oscillating said shaft.
 9. The screening apparatus of claim 1 wherein said modular side frame sections include a side wall and an inwardly extending flange along the upper edge of said side wall for supporting the longitudinal edge of said screen cloth, and tension means connected between opposite ends of said screen cloth and the adjacent cross member for exerting adjustable longitudinal tension on said screen cloth.
 10. The screening apparatus of claim 9 including a screen vibrating mechanism supported by a pair of opposite modular side sections on opposite sides of said frame, said mechanism including means engaging the under side of said screen cloth for vibrating the same up and down.
 11. A screening apparatus for classifying materials comprising a screen cloth supported from a frame of variable size, said frame comprising a pair of end cross members interconnecting the ends of a plurality of pairs of modular side frame sections on opposite sides of said frame joined end to end, each side frame section including a side wall and a pair of end walls having parallel outer end faces normal to said side wall, and screen vibrator means supported from a pair of opposite side frame sections independent of other sections.
 12. The screening apparatus of claim 11 wherein each modular side frame section has a channel shaped cross section including a pair of upper and lower flanges extending outwardly of the edges of said side wall and joined at opposite ends with said end walls forming an outwardly opening enclosure, said screen vibrating means including an oscillatory shaft extending between opposite side frame sections and a pair of bearings supporting opposite ends of said shaft mounted in said enclosures of said opposite side frame sections on a portion of the flange thereof.
 13. The screening apparatus of claim 12 wherein said vibrator means includes A reciprocating vibrator mounted on the flange of one of said pairs of opposite side frame sections and connector means interconnecting said vibrator and an end portion of said shaft to rotatively oscillate the same upon reciprocation of said vibrator.
 14. The screening apparatus of claim 13 wherein said bearings are mounted on the underside of said upper flanges and said vibrator is mounted on the top of an upper flange, said vibrator including a reciprocating armature extended through an opening in said upper flange and pivotally connected at its lower end to said connector means. 